SORVEGLIANZA DELLA CIRCOLAZIONE DI POLIOVIRUS NELLA POPOLAZIONE LOMBARDA NELL'AMBITO DEL PROGETTO DI ERADICAZIONE MONDIALE DELLA POLIOMIELITE

Poliomyelitis is an acute, viral, infectious disease caused by the 3 poliovirus that spread from person to person, primarily via the fecal-oral route. Although approximately 90% of polio infections cause no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream. In about 1% of cases, the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Polio had existed for thousands of years quietly as an endemic pathogen until the 1880s, when major epidemics began to occur in Europe; soon after, widespread epidemics appeared in the United States. But following the widespread use of poliovirus vaccine in the mid-1950s, the incidence of poliomyelitis declined dramatically in many industrialized countries. A global effort to eradicate polio began in 1988, led by the World Health Organization, UNICEF, and The Rotary Foundation. These efforts have reduced the number of annual diagnosed cases by more than 99%; from an estimated 350,000 cases in 1988 to 215 cases in 2012, the lowest ever recorded. Stopping poliovirus transmission is pursued through a combination of high infant immunization coverage and surveillance for wild poliovirus through reporting and laboratory testing of all cases of acute flaccid paralysis (AFP) among children less than fifteen years of age. Since 1997 in Lombardy the AFP surveillance Regional Reference Center (RCC) is located in the Department of Biomedical Sciences for Health ex Department of Microbiology-Virology-Public Health and its activity is coordinated by the National Institute of Health (ISS) and the Ministry of Health (MOH). To conduct surveillance RCC established and still coordinates a network of hospital referents that deal with the reporting of AFP cases in children under fifteen years old even in the absence of cases. Since 1997, the number of hospitals participating has increased up to 51 in 2012. As the RCC is provided with an accredited laboratory it also carries out the virological investigations on biological samples. Laboratory analysis mainly consists in the detection of polioviruses by isolation in cell culture (RD and L20B) of two faecal samples that must be collected within 14 days after the onset of paralysis. The RCC also deals with the environmental monitoring which consists in the collection and analysis of sewage samples, collected at two sites (Nosedo and Peschiera Borromeo) of the center-east Lombard sewer network. The laboratory analysis is the detection of polioviruses and other non-polio enterovirus by isolation in cell culture. During the period 2010-2012 the AFP surveillance identified 27 cases and 185 sewage samples has been collected as regards the environmental surveillance. No virological and environmental samples were tested poliovirus positive. In none of the three years the goal of the 14 AFP expected cases was achieved and also other performance indicators are proving poor that shows cases are often not promptly and properly reported even if stool samples have been collected in almost the cases. Instead the high percentage (79%) of non-polio enterovirus positive samples of sewage emphasizes high circulation of non-polio enterovirus in the Lombard population and confirms the good quality of the conducted investigations. It is important to guarantee a high quality surveillance as there is a risk of importation of cases from areas where polio is endemic. The surveillance activities will continue long after the eradication of poliomyelitis to guarantee the effective stopping of both wild and vaccine-derived poliovirus circulation.